One of the advantages of mirrorless cameras is their compact size. But what if a DSLR camera is about the size of a mirrorless camera? Enter the Pentax KP.

If you put the KP side by side with Sony's A7R II, there is no considerable difference in their sizes.

Granted that the A7R II has a full-frame image sensor while the KP packs a 24.3-megapixel APS-C image sensor, but it is still quite amazing that Pentax has managed to pack everything into such a small package.

That said, its design does seem a bit odd. The mirror box is quite big compared with its sides. This is because the mirror box is about the same size as those in most APS-C DSLR cameras but the KP has an overall narrower front profile compared with them.

To compensate for that, Pentax has made the KP's grip interchangeable. All you need to do is to use a hexagonal key to unmount the grip and change to another one.

The camera comes fitted with the small grip, which felt a tad small in my palm. Pentax also sells grips in medium and large sizes.

I found the camera's build to be sturdy. It is also reassuring to know that the KP's magnesium-alloy body is supposed to be resistant to water, fog, snow, sand and dust.

But what I really like about the KP is the button layout. It has taken some cues from Pentax's flagship DSLR camera, the K-1. For example, on the KP's top left is a Mode dial that can store five user modes, alongside the usual aperture-priority and shutter-priority modes.

On the top right is an extra Multi Function dial with markings such as ISO and Wi-Fi, and there is another command dial beside it. These two dials give you quick access to change ISO, Wi-Fi, High Dynamic Range (HDR) and other functions.

Here, you will also find a lever switch that lets you toggle through the various shooting modes - still image, live view and video - easily.

But, unlike the K-1, the KP has a vertically mounted front control dial, which stands out from the half-hidden front dial of many other DSLR cameras. I found this vertical dial to be more comfortable and intuitive to use than the common front one.

My only gripe is that there is no mini-joystick that lets you change the autofocusing (AF) point. Otherwise, the button layout would have been perfect.

The KP's operation is quite fast. I found starting up and shutting down the camera to be immediate.

However, using an SD card with a writing speed of 95MB per second, the KP was only able to capture six RAW images in 0.9sec before the buffer ran out.

For this review, I used the Pentax 18-135mm f/3.5-5.6 lens with the KP. Its AF was instantaneous in bright sunlight. In dim lighting conditions, it took at most 2sec to secure a focus with the aid of AF- assist light.

On the downside, you need to press the rear AF button to get a focus when you pan from one scene to another during video recording. At times, it might not even secure a focus - certainly not the camera to get if you want to shoot more videos.

Still images, though, look superb with very sharp pixel rendition and vivid colour reproduction. Details are crisp and smooth. The dynamic range is great and images look natural.

One of the highlights of the KP is its ability to go up to the staggeringly high sensitivity setting of ISO 819,200. However, you will use this setting only in desperate times because the result is like a botched water-colour painting.

In fact, I wouldn't recommend shooting at ISO 25,600 and above, because of the abundance of chromatic noise that crops up in photos.

But you will not notice any image noise until ISO 3,200, with loss of details becoming more evident only at ISO 6,400. Even at ISO 12,800, images are still good enough for Web use.

The biggest downer of the KP is its rather mediocre battery life. Most mid-range DSLR cameras can go up to 500 to 600 images on a full charge. But the KP can shoot up to only around 400 still images before the fully charged battery goes flat.

• Verdict: If you are a Pentaxian who could not afford the full-frame K-1, the Pentax KP is a more affordable but yet very capable option.